Umm, not sure why it's forcing the GMail app, but when you add an account through the phone's settings (not through the app), it should use the default e-mail app for that.
But for Exchange I'd suggest you use Nine. It's a paid app, but well worth the 9 bucks. Once I tried it I never looked back (used to stick to the stock app for work e-mail... not anymore)
Is it a company-provided Exchange account? If so, the company can dictate which app to use based on security testing and any other app would be blocked. There are lots of apps that could work with Exchange - one that comes to mind is named "Nine". Are there any particular features you seek that might help others direct their suggestions to your needs/wants?
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